primary treated wastewater Eirini F. Barkonikou, AndrianaF. - - PowerPoint PPT Presentation

Eirini F. Barkonikou, AndrianaF. Aravantinou, and Ioannis D. Manariotis

Environmental Engineering Laboratory Department of Civil Engineering

Microalgae biomass growth and lipid production using primary treated wastewater

• Introduction - Microalgae & Wastewater treatment
• Materials and Methods
• Results - Biomass production
• Nutrients removal
• Lipid production
• Conclusions

The aim of this study was to evaluate the algal production in a laboratory scale open pond using as a feedstock primary treated wastewater. To further improve the nutrient removal from wastewater and to investigate the potential production of biomass as as renewable energy source.

 Microalgae and wastewater treatment:  Natural treatment systems (sewage lagoons/sewage farms, stabilization

ponds, other algal reactors). The first farm for the treatment of sewage with algae was reported in late 1800s in Berlin.

 Wastewater treatment with algae offers important advantages:

• low capital and operation cost
• low energy requirements
• contribution to reduction of CO2 emissions
• use of algal biomass as fertilizer or fuel source
• great potential for algae to be used as biofuels.

Introduction

Introduction



The selection of microalgae for potential biofuel production should take into consideration the:

• high algal cell density,
• high lipids content,
• but also their presence and survival in wastewater.



What does affect algal growth?  Nutrients concentration, especially P and N  Aeration rate  Light conditions  Temperature  CO2CO2  pH

In UPEEL

• Identification of suitable species and cultivation system
• Determination of microalgae growth rates

Aravantinou et al. (2013). Bioresource Technology, 147 (130-134).

In UPEEL

(University of Patras, Environmental Engineering Laboratory)

• Culture optimization
• Short-term toxicity of nanoparticles
• n microalgae growth Aravantinou et al.

(2015). Ecotoxicology and Environmental Safety.

• Microalgae harvesting

Vergini et al. (2016) Journal of Applied Phycology

• Scale-up

Aravantinou et al. (2016) Environmental Processes

8

Six sets of experiments were conducted with primary treated wastewater in batch and continuous operating mode. The culture was exposed to artificial light 100 μmol/m2s. In the last set the radiation intensity was set to 200 μmol/m2s. Phase Operation mode Flow rate HRT (days) 1 Batch

• 2

Fill and draw 1 L/d 30 3 Continuous 1 L/d 30 4 Batch

• 5*

Batch

• 6**

Continuous 1 L/d 30

* Addition of PO4

• 3.

**Radiation intensity: 200 μmol/m2s.

Experimental conditions Investigating parameters

• Laboratory- scale open pond:

50x50x25 cm (LxWxH)

• Pre-cultured cells and secondary treated

wastewater

• Working volume: 30 L
• Temperature: 21 ± 2 οC
• Photoperiod: 12 h: 12 h (dark: light)
• Air supply: 2 L/min
• Operation period: 14 to 33 d
• Operation mode: Batch, Fill and Draw

Continuous

• Flow rate/ Hydraulic Retention Time
• Photosynthetic radiation intensity:

100, 200 μmol·m-2·s-1

• Wastewater: Primary effluent

Parameter Method Biomass

• Gravimetric method, Total suspended solids
• Absorbance (750 nm)
• Chl-a (APHA et al., 1998)
• Turbidity (NTU)

Total - N Method 2,6- dimethylphenol (ISO 7890/1) Nitrates Ion Chromatography (APHA et al., 1998) Total - P Persulfate digestion and ascorbic acid method (APHA et al., 1998) Phosphates Ion Chromatography (APHA et al., 1998) COD Method 410.4 (O’ Dell, 1993) Soluble non-purgeable organic carbon TOC analyzer (APHA et al., 1998) pH pH-meter Lipid extraction Method of Folch et al. (1957)

Biomass concentration

Primary treated wastewater

Phase 1 Phase 2 Phase 3 Phase 4 Phase 5 Phase 6 Mode Batch Fill & Draw Continuous Batch Batch Continuous Radiation 100 μmol/m2s 100 μmol/m2s 100 μmol/m2s 100 μmol/m2s 200 μmol/m2s



The growth rate of algae was affected by light intensity.



The maximum biomass concentration of 449 mg/L was observed under continuous mode and high radiation intensity in phase 6.



Although the light intensity is an important factor in algae growth, the nutrient concentration, which was fed in the pond, is more important for algae growth.

Nitrates

Primary treated wastewater

Phase 1 Phase 2 Phase 3 Phase 4 Phase 5 Phase 6 Mode Batch Fill & Draw Continuous Batch Batch Continuous Radiation 100 μmol/m2s 100 μmol/m2s 100 μmol/m2s 100 μmol/m2s 200 μmol/m2s



Microalgae can assimilate a significant amount of nutrients in excess of the immediate metabolic needs.



The nitrate removal was satisfactory, and the maximum decrease of nitrates concentration (76%) was observed the same day with the external addition of phosphorus on day 14 (Phase 5).

Phosphates

Primary treated wastewater

Phase 1 Phase 2 Phase 3 Phase 4 Phase 5 Phase 6 Mode Batch Fill & Draw Continuous Batch Batch Continuous Radiation 100 μmol/m2s 100 μmol/m2s 100 μmol/m2s 100 μmol/m2s 200 μmol/m2s



Phosphates as well as nitrates are essential nutrients for biomass growth.



Phosphates concentration in the influent ranged from 0.60 to 1.57 mg P/L and in the effluent their concentration was almost zero, implying the complete removal of phosphates.

Lipid content

Primary treated wastewater

Phase 1 Phase 2 Phase 3 Phase 4 Phase 5 Phase 6 Mode Batch Fill & Draw Continuous Batch Batch Continuous Radiation 100 μmol/m2s 100 μmol/m2s 100 μmol/m2s 100 μmol/m2s 200 μmol/m2s



The lipid content was affected by the influent nutrient concentration, and higher values were observed with low nitrates concentration in the influent.



Nutrients removal and the impact of nutrients concentration on the lipid content

• f algal cells is an essential step before the scale-up of biomass and lipid

production by microalgae.

 The algal production was satisfactory in a laboratory open

pond, which was fed with primary treated wastewater.

 Microalgal growth was affected by phosphates concentration

and irradiation intensity.

 The efficiency of microalgae to remove nitrates and phosphates

was satisfactory, and reached removals of 76 and almost 100%, respectively.

 Finally, the highest lipid content was 15% when the microalgae

faced starvation conditions.

 Scale-up of ponds with microalgae species with higher lipid

content i.e. Scenedesmus rubescens.

 Cultivation of high lipid microalgae in outdoor ponds for

wastewater treatment.

 Investigation of low-cost harvesting method for microalgae

biomass (magnetic microparticles, electrocoagulation, flocculation etc.)

 Long-term impact of nanoparticles on microalgae cultures.

Th Thank k you for r your r attention tention !!! !!